The present invention relates to elevator systems having flat belts supporting the elevator car.
Elevator systems of the kind according to the present invention usually comprise an elevator car and a counterweight, which are movable in an elevator shaft or along free-standing guide devices. For producing movement, the elevator system comprises at least one drive with at least one respective drive pulley which by way of support and drive means supports the elevator car and the counterweight and transmits the necessary drive forces to these.
The support or the drive means are termed support means in the following description.
In the case of conventional elevator systems, steel cables with a round cross-section are usually used as support means. However, flat belt-like support means are increasingly used for more modem systems.
An elevator system with a flat-belt-like support means is shown in the PCT Patent Application WO 99/43593. In the embodiment illustrated therein by FIG. 6 the elevator system comprises a drive motor which is arranged in the elevator shaft above the elevator car and acts by way of at least one drive pulley on at least one flat support means strand by which an elevator car and a counterweight arranged on the side thereof can be moved upwardly and downwardly. The flat-belt-like support means in that case runs from one side of the drive pulley horizontally to a first deflecting roller, runs around this through 90°, then extends downwardly along the car wall at the counterweight side, loops by 90° around each of two car support rollers mounted on respective sides below the elevator car and runs upwardly along a car wall remote from the counterweight to a first support means fixing point present in the upper region of the elevator shaft. From the other side of the drive pulley the support means runs horizontally to a second deflecting roller, runs around this by 90°, then extends downwardly to the side, which is at the car side, of the periphery of a counterweight support roller, loops around this by 180° and runs vertically to a second support means fixing point in the shaft head region.
Such an elevator system has, thanks to the use of a flat-belt-like support means, the advantage that drive pulleys as well as deflecting and support rollers can be used with substantially smaller diameters than would be required in the case of the use of conventional wire cables. Due to the smaller drive pulley diameter the drive torque required at the drive pulley is reduced, whereby a drive motor with smaller dimensions can be used. Thanks to the generally smaller support means pulley diameter it is possible to realize simpler and space-saving elevator systems.
However, the elevator systems described in the WO 99/43593 publication have certain disadvantages.
As a consequence of the small drive pulley diameter, and because in the case of use of flat belts as support means known measures for improving the traction capability, for example undercutting of the cable grooves at drive pulleys for round support means, are not usable, the problem can arise in the case of a relatively large weight ratio between fully laden and empty elevator car that the traction forces transmissible between drive pulley and flat-belt-like traction means are not sufficient.
Moreover, it is known that in the case of use of flat-belt-like support means without profiling of the running surface substantial problems with the lateral guidance of the support means on the drive pulley, deflecting rollers and the support rollers arise. Experience has shown that there is a risk that the support means so strongly rubs against the lateral boundary discs usually present at the drive pulleys, deflecting rollers and support rollers that the support means are damaged.